Visual studio 2015 compilation

Created by: ZuBsPaCe

With these changes I'm able to build godot successfully like this:

c:\python27\scripts\scons.bat vsproj=yes platform=windows -j8

For parallel builds, you need the pywin32 extensions. This reduces build time by a factor of 3 on my machine, which is a godsend! (3 instead of 9 minutes for a full rebuild). This resulted in an error before.

Everything works fine. A single *.pdb gets generated. release_debug builds with tools included are running fine. The executable has a size of 15.2 MB, which is quite smaller than the older builds. This is because there was a linker error which forced me to link to the c runtime dynamically. But this should be preferred anyway.

For reference: I'm Using Visual Studio 2015 Enterprise on Windows 10.

I remember, that there was a problem when Visual Studio 2013 and 2015 were installed on the same machine. Could be an error with scons. But I got a new notebook and just got 2015 installed. So keep that in mind.